1. Field of the Invention
The present invention is generally related to communication systems. More particularly, the present invention is related to a cable modem system, method and computer program product for optimizing the transmission of TCP/IP traffic across a DOCSIS network.
2. Background Art
Conventional cable modem systems utilize DOCSIS (Data Over Cable System Interface Specification)—compliant equipment and protocols to transfer data between one or more cable modems (CM) and a cable modem termination system (CMTS). DOCSIS generally refers to a group of specifications that define industry standards for cable headend and cable modem equipment. In part, DOCSIS sets forth requirements and objectives for various aspects of cable modem systems including operations support systems, management, data interfaces, as well as network layer, data link layer, and physical layer transport for cable modem systems.
DOCSIS 1.1 enables the suppression of redundant information in packets with a feature called “payload header suppression” (PHS). PHS in DOCSIS enables the suppression of unchanging bytes in an upstream data stream for a specific cable modem (CM) (i.e., SID). This PHS feature is designed primarily for fixed length, unchanging packet types. It is a byte-oriented suppression mechanism that supports any protocol that could be transmitted on the DOCSIS network.
DOCSIS PHS's byte oriented suppression is not as efficient as a field oriented protocol header suppression scheme. The header bytes are different for each TCP connection. Also, DOCSIS PHS cannot efficiently handle multiple TCP connections within the same data stream, i.e., Service Identifier (SID), which is the usual application case. This limitation could be somewhat overcome by reserving multiple header suppression rules for each TCP session on a SID. Unfortunately, this approach consumes CMTS resources, and is not very efficient.
DOCSIS PHS rule modification requires a full duplex command transaction between the cable modem (CM) and the cable modem termination system (CMTS). To effectively suppress TCP/IP traffic using DOCSIS PHS, the suppression rule must be updated each time the header changes, thereby causing a delay. In a TCP/IP data stream, this delay will significantly reduce the header suppression efficiency because packets must be transmitted without suppression until the rule modification is confirmed by the CMTS.
DOCSIS PHS techniques cannot suppress dynamically changing fields. TCP header fields like “ACK”, “SEQUENCE NUMBER”, and “WINDOW SIZE” change often during a TCP/IP connection session. These fields are not suppressable under DOCSIS PHS rules.
DOCSIS cable modem networks are designed to handle 802.3 (Ethernet) style traffic. The typical traffic pattern on a DOCSIS network is TCP/IP, of which web browsing, electronic mail, and ftp transfers are the largest part. Most of the packets transmitted in the upstream direction of a DOCSIS network are TCP Acknowledgements (ACKS). Being an 802.3 style transport, the DOCSIS protocol does not handle TCP Acknowledgements and the like very efficiently.
What is needed is a system, method, and computer program product for recognizing and optimizing the transmission of TCP/IP style traffic across a DOCSIS network. What is further needed is a system, method, and computer program product for recognizing and optimizing the transmission of TCP/IP style traffic across a DOCSIS network that handles changing and unchanging fields between TCP protocol packets in a TCP connection stream.